you can get away with as little as a kettle for boiling wort, a fermentor setup (bucket, lid, airlock), and some stuff for bottling (siphon/hose, bottling wand, bottles, caps, and a capping tool if using glass bottles). That will allow you to start brewing extract-based beers. The next logical step is BIAB, which is the same setup except you add in a bag to hold grains and your process adds the mashing step.

I'd recommend getting at least a couple extract brews under your belt, then upgrading your setup. Prices and where to buy depends on where you are, but there's plenty of shops throughout North America (and EU/Aus/etc) that sell equipment kits